There are two people who wouldn't know where there healers are: flankers, and tricklers.

Genjis, Tracers, and Sombras should be self sufficient. They're supposed to be behind enemy lines. And if they need an Ana pocket to kill the Zen, or they are taking duels they can't handle, then they need to consider a different role. Any healing darts or orbs they get are pure gratuity.

Other DPS are (read: ought to be) playing around the tanks. Incidentally, this is where the healers like to be. No problem.

Tricklers are going to die, and the sooner they do the better, as it they might catch the rest of the team coming back from spawn. Healers don't risk themselves to save tricklers who overextended. And tricklers don't need to see healers when they have the kill feed and can just look around.